three.js/examples/js/loaders/LWOLoader.js

/**
 * @author Lewy Blue https://github.com/looeee
 *
 * Load files in LWO3 and LWO2 format
 *
 * LWO3 format specification:
 * 	http://static.lightwave3d.com/sdk/2018/html/filefmts/lwo3.html
 *
 * LWO2 format specification:
 * 	http://static.lightwave3d.com/sdk/2018/html/filefmts/lwo2.html
 *
 */

THREE.LWOLoader = ( function () {

	var lwoTree;

	function LWOLoader( manager ) {

		this.manager = ( manager !== undefined ) ? manager : THREE.DefaultLoadingManager;

	}

	LWOLoader.prototype = {

		constructor: LWOLoader,

		crossOrigin: 'anonymous',

		load: function ( url, onLoad, onProgress, onError ) {

			var self = this;

			var path = ( self.path === undefined ) ? THREE.LoaderUtils.extractUrlBase( url ) : self.path;

			// give the mesh a default name based on the filename
			var modelName = url.split( path ).pop().split( '.' )[ 0 ];

			var loader = new THREE.FileLoader( this.manager );
			loader.setPath( self.path );
			loader.setResponseType( 'arraybuffer' );

			loader.load( url, function ( buffer ) {

				// console.time( 'Total parsing: ' );
				onLoad( self.parse( buffer, path, modelName ) );
				// console.timeEnd( 'Total parsing: ' );

			}, onProgress, onError );

		},

		setCrossOrigin: function ( value ) {

			this.crossOrigin = value;
			return this;

		},

		setPath: function ( value ) {

			this.path = value;
			return this;

		},

		setResourcePath: function ( value ) {

			this.resourcePath = value;
			return this;

		},

		parse: function ( iffBuffer, path, modelName ) {

			lwoTree = new IFFParser().parse( iffBuffer );

			// console.log( 'lwoTree', lwoTree );

			var textureLoader = new THREE.TextureLoader( this.manager ).setPath( this.resourcePath || path ).setCrossOrigin( this.crossOrigin );

			return new LWOTreeParser( textureLoader ).parse( modelName );

		}

	};

	// Parse the lwoTree object
	function LWOTreeParser( textureLoader ) {

		this.textureLoader = textureLoader;

	}

	LWOTreeParser.prototype = {

		constructor: LWOTreeParser,

		parse: function ( modelName ) {

			this.materials = new MaterialParser( this.textureLoader ).parse();
			this.defaultLayerName = modelName;

			this.meshes = this.parseLayers();

			return {
				materials: this.materials,
				meshes: this.meshes,
			};

		},

		parseLayers() {

			// array of all meshes for building hierarchy
			var meshes = [];

			// final array containing meshes with scene graph hierarchy set up
			var finalMeshes = [];

			var geometryParser = new GeometryParser();

			var self = this;
			lwoTree.layers.forEach( function ( layer ) {

				var geometry = geometryParser.parse( layer.geometry, layer );

				var mesh = self.parseMesh( geometry, layer );

				meshes[ layer.number ] = mesh;

				if ( layer.parent === - 1 ) finalMeshes.push( mesh );
				else meshes[ layer.parent ].add( mesh );


			} );

			this.applyPivots( finalMeshes );

			return finalMeshes;

		},

		parseMesh( geometry, layer ) {

			var mesh;

			var materials = this.getMaterials( geometry.userData.matNames, layer.geometry.type );

			this.duplicateUVs( geometry, materials );

			if ( layer.geometry.type === 'points' ) mesh = new THREE.Points( geometry, materials );
			else if ( layer.geometry.type === 'lines' ) mesh = new THREE.LineSegments( geometry, materials );
			else mesh = new THREE.Mesh( geometry, materials );

			if ( layer.name ) mesh.name = layer.name;
			else mesh.name = this.defaultLayerName + '_layer_' + layer.number;

			mesh.userData.pivot = layer.pivot;

			return mesh;

		},

		// TODO: may need to be reversed in z to convert LWO to three.js coordinates
		applyPivots( meshes ) {

			meshes.forEach( function ( mesh ) {

				mesh.traverse( function ( child ) {

					var pivot = child.userData.pivot;

					child.position.x += pivot[ 0 ];
					child.position.y += pivot[ 1 ];
					child.position.z += pivot[ 2 ];

					if ( child.parent ) {

						var parentPivot = child.parent.userData.pivot;

						child.position.x -= parentPivot[ 0 ];
						child.position.y -= parentPivot[ 1 ];
						child.position.z -= parentPivot[ 2 ];

					}

				} );

			} );

		},

		getMaterials( namesArray, type ) {

			var materials = [];

			var self = this;

			namesArray.forEach( function ( name, i ) {

				materials[ i ] = self.getMaterialByName( name );

			} );

			// convert materials to line or point mats if required
			if ( type === 'points' || type === 'lines' ) {

				materials.forEach( function ( mat, i ) {

					var spec = {
						color: mat.color,
					};

					if ( type === 'points' ) {

						spec.size = 0.1;
						spec.map = mat.map;
						spec.morphTargets = mat.morphTargets;
						materials[ i ] = new THREE.PointsMaterial( spec );

					} else if ( type === 'lines' ) {

						materials[ i ] = new THREE.LineBasicMaterial( spec );

					}

				} );

			}

			// if there is only one material, return that directly instead of array
			var filtered = materials.filter( Boolean );
			if ( filtered.length === 1 ) return filtered[ 0 ];

			return materials;

		},

		getMaterialByName( name ) {

			return this.materials.filter( function ( m ) {

				return m.name === name;

			} )[ 0 ];

		},

		// If the material has an aoMap, duplicate UVs
		duplicateUVs( geometry, materials ) {

			var duplicateUVs = false;

			if ( ! Array.isArray( materials ) ) {

				if ( materials.aoMap ) duplicateUVs = true;

			} else {

				materials.forEach( function ( material ) {

					if ( material.aoMap ) duplicateUVs = true;

				} );

			}

			if ( ! duplicateUVs ) return;

			geometry.addAttribute( 'uv2', new THREE.BufferAttribute( geometry.attributes.uv.array, 2 ) );

		},

	};

	function MaterialParser( textureLoader ) {

		this.textureLoader = textureLoader;

	}

	MaterialParser.prototype = {

		constructor: MaterialParser,

		parse: function () {

			var materials = [];
			this.textures = {};

			for ( var name in lwoTree.materials ) {

				if ( lwoTree.format === 'LWO3' ) {

					materials.push( this.parseMaterial( lwoTree.materials[ name ], name, lwoTree.textures ) );

				} else if ( lwoTree.format === 'LWO2' ) {

					materials.push( this.parseMaterialLwo2( lwoTree.materials[ name ], name, lwoTree.textures ) );

				}

			}

			return materials;

		},

		parseMaterial( materialData, name, textures ) {

			var params = {
				name: name,
				side: this.getSide( materialData.attributes ),
				flatShading: this.getSmooth( materialData.attributes ),
			};

			var connections = this.parseConnections( materialData.connections, materialData.nodes );

			var maps = this.parseTextureNodes( connections.maps );

			this.parseAttributeImageMaps( connections.attributes, textures, maps, materialData.maps );

			var attributes = this.parseAttributes( connections.attributes, maps );

			this.parseEnvMap( connections, maps, attributes );

			params = Object.assign( maps, params );
			params = Object.assign( params, attributes );

			var type = connections.attributes.Roughness ? 'Standard' : 'Phong';

			return new THREE[ 'Mesh' + type + 'Material' ]( params );

		},

		parseMaterialLwo2( materialData, name, textures ) {

			var params = {
				name: name,
				side: this.getSide( materialData.attributes ),
				flatShading: this.getSmooth( materialData.attributes ),
			};

			var attributes = this.parseAttributes( materialData.attributes, {} );
			params = Object.assign( params, attributes );
			return new THREE[ 'MeshPhongMaterial' ]( params );

		},

		// Note: converting from left to right handed coords by switching x -> -x in vertices, and
		// then switching mat FrontSide -> BackSide
		// NB: this means that THREE.FrontSide and THREE.BackSide have been switched!
		getSide( attributes ) {

			if ( ! attributes.side ) return THREE.BackSide;

			switch ( attributes.side ) {

				case 0:
				case 1:
					return THREE.BackSide;
				case 2: return THREE.FrontSide;
				case 3: return THREE.DoubleSide;

			}

		},

		getSmooth( attributes ) {

			if ( ! attributes.smooth ) return true;
			return ! attributes.smooth;

		},

		parseConnections( connections, nodes ) {

			var materialConnections = {
				maps: {}
			};

			var inputName = connections.inputName;
			var inputNodeName = connections.inputNodeName;
			var nodeName = connections.nodeName;

			var self = this;
			inputName.forEach( function ( name, index ) {

				if ( name === 'Material' ) {

					var matNode = self.getNodeByRefName( inputNodeName[ index ], nodes );
					materialConnections.attributes = matNode.attributes;
					materialConnections.envMap = matNode.fileName;
					materialConnections.name = inputNodeName[ index ];

				}

			} );

			nodeName.forEach( function ( name, index ) {

				if ( name === materialConnections.name ) {

					materialConnections.maps[ inputName[ index ] ] = self.getNodeByRefName( inputNodeName[ index ], nodes );

				}

			} );

			return materialConnections;

		},

		getNodeByRefName( refName, nodes ) {

			for ( var name in nodes ) {

				if ( nodes[ name ].refName === refName ) return nodes[ name ];

			}

		},

		parseTextureNodes( textureNodes ) {

			var maps = {};

			for ( var name in textureNodes ) {

				var node = textureNodes[ name ];
				var path = node.fileName;

				if ( ! path ) return;

				var texture = this.loadTexture( path );

				if ( node.widthWrappingMode !== undefined ) texture.wrapS = this.getWrappingType( node.widthWrappingMode );
				if ( node.heightWrappingMode !== undefined ) texture.wrapT = this.getWrappingType( node.heightWrappingMode );

				switch ( name ) {

					case 'Color':
						maps.map = texture;
						break;
					case 'Roughness':
						maps.roughnessMap = texture;
						maps.roughness = 0.5;
						break;
					case 'Specular':
						maps.specularMap = texture;
						maps.specular = 0xffffff;
						break;
					case 'Luminous':
						maps.emissiveMap = texture;
						maps.emissive = 0x808080;
						break;
					case 'Metallic':
						maps.metalnessMap = texture;
						maps.metalness = 0.5;
						break;
					case 'Transparency':
					case 'Alpha':
						maps.alphaMap = texture;
						maps.transparent = true;
						break;
					case 'Normal':
						maps.normalMap = texture;
						if ( node.amplitude !== undefined ) maps.normalScale = new THREE.Vector2( node.amplitude, node.amplitude );
						break;
					case 'Bump':
						maps.bumpMap = texture;
						break;

				}

			}

			// LWO BSDF materials can have both spec and rough, but this is not valid in three
			if ( maps.roughnessMap && maps.specularMap ) delete maps.specularMap;

			return maps;

		},

		// maps can also be defined on individual material attributes, parse those here
		// This occurs on Standard (Phong) surfaces
		parseAttributeImageMaps( attributes, textures, maps ) {

			for ( var name in attributes ) {

				var attribute = attributes[ name ];

				if ( attribute.maps ) {

					var mapData = attribute.maps[ 0 ];

					var path = this.getTexturePathByIndex( mapData.imageIndex, textures );
					if ( ! path ) return;

					var texture = this.loadTexture( path );

					if ( mapData.wrap !== undefined ) texture.wrapS = this.getWrappingType( mapData.wrap.w );
					if ( mapData.wrap !== undefined ) texture.wrapT = this.getWrappingType( mapData.wrap.h );

					switch ( name ) {

						case 'Color':
							maps.map = texture;
							break;
						case 'Diffuse':
							maps.aoMap = texture;
							break;
						case 'Roughness':
							maps.roughnessMap = texture;
							maps.roughness = 1;
							break;
						case 'Specular':
							maps.specularMap = texture;
							maps.specular = 0xffffff;
							break;
						case 'Luminosity':
							maps.emissiveMap = texture;
							maps.emissive = 0x808080;
							break;
						case 'Metallic':
							maps.metalnessMap = texture;
							maps.metalness = 1;
							break;
						case 'Transparency':
						case 'Alpha':
							maps.alphaMap = texture;
							maps.transparent = true;
							break;
						case 'Normal':
							maps.normalMap = texture;
							break;
						case 'Bump':
							maps.bumpMap = texture;
							break;

					}

				}

			}

		},

		parseAttributes( attributes, maps ) {

			var params = {};

			// don't use color data if color map is present
			if ( attributes.Color && ! maps.map ) {

				params.color = new THREE.Color().fromArray( attributes.Color.value );

			} else params.color = new THREE.Color();


			if ( attributes.Transparency && attributes.Transparency.value !== 0 ) {

				params.opacity = 1 - attributes.Transparency.value;
				params.transparent = true;

			}

			if ( attributes[ 'Bump Height' ] ) params.bumpScale = attributes[ 'Bump Height' ].value * 0.1;

			if ( attributes[ 'Refraction Index' ] ) params.refractionRatio = 1 / attributes[ 'Refraction Index' ].value;

			this.parseStandardAttributes( params, attributes, maps );
			this.parsePhongAttributes( params, attributes, maps );

			return params;

		},

		parseStandardAttributes( params, attributes, maps ) {

			if ( attributes.Luminous && attributes.Luminous.value !== 0 && attributes[ 'Luminous Color' ] ) {

				var emissiveColor = attributes[ 'Luminous Color' ].value.map( function ( val ) {

					return val * attributes.Luminous.value;

				} );

				params.emissive = new THREE.Color().fromArray( emissiveColor );

			}
			if ( attributes.Roughness && ! maps.roughnessMap ) params.roughness = attributes.Roughness.value;
			if ( attributes.Metallic && ! maps.metalnessMap ) params.metalness = attributes.Metallic.value;

		},

		parsePhongAttributes( params, attributes, maps ) {

			if ( attributes.Diffuse ) params.color.multiplyScalar( attributes.Diffuse.value );

			if ( attributes.Reflection ) {

				params.reflectivity = attributes.Reflection.value;
				params.combine = THREE.AddOperation;

			}

			if ( attributes.Luminosity && ! maps.emissiveMap ) params.emissive = new THREE.Color().setScalar( attributes.Luminosity.value );

			if ( attributes.Glossiness !== undefined ) params.shininess = 5 + Math.pow( attributes.Glossiness.value * 7, 6 );

			// parse specular if there is no roughness - we will interpret the material as 'Phong' in this case
			if ( ! attributes.Roughness && attributes.Specular && ! maps.specularMap ) params.specular = new THREE.Color().setScalar( attributes.Specular.value * 1.5 );

		},

		parseEnvMap( connections, maps, attributes ) {

			if ( connections.envMap ) {

				var envMap = this.loadTexture( connections.envMap );

				if ( attributes.transparent && attributes.opacity < 0.999 ) {

					envMap.mapping = THREE.EquirectangularRefractionMapping;

					// Reflectivity and refraction mapping don't work well together in Phong materials
					if ( attributes.reflectivity !== undefined ) {

						delete attributes.reflectivity;
						delete attributes.combine;

					}

					if ( attributes.metalness !== undefined ) {

						delete attributes.metalness;

					}

				} else envMap.mapping = THREE.EquirectangularReflectionMapping;

				maps.envMap = envMap;

			}

		},

		// get texture defined at top level by its index
		getTexturePathByIndex( index ) {

			var fileName = '';

			if ( ! lwoTree.textures ) return fileName;

			lwoTree.textures.forEach( function ( texture ) {

				if ( texture.index === index ) fileName = texture.fileName;

			} );

			return fileName;

		},

		loadTexture( path ) {

			if ( ! path ) return null;

			return this.textureLoader.load( this.cleanPath( path ) );

		},

		// Lightwave expects textures to be in folder called Images relative
		// to the model
		// Otherwise, the full absolute path is stored: D://some_directory/textures/bumpMap.png
		// In this case, we'll strip out everything and load 'bumpMap.png' from the same directory as the model
		cleanPath( path ) {

			if ( path.indexOf( 'Images' ) === 0 || path.indexOf( 'images' ) === 0 ) return './' + path;
			return path.split( '/' ).pop().split( '\\' ).pop();

		},

		// 0 = Reset, 1 = Repeat, 2 = Mirror, 3 = Edge
		getWrappingType( num ) {

			switch ( num ) {

				case 0:
					console.warn( 'LWOLoader: "Reset" texture wrapping type is not supported in three.js' );
					return THREE.ClampToEdgeWrapping;
				case 1: return THREE.RepeatWrapping;
				case 2: return THREE.MirroredRepeatWrapping;
				case 3: return THREE.ClampToEdgeWrapping;

			}

		},

		getType( nodeData ) {

			if ( nodeData.roughness ) return 'Standard';
			return 'Phong';

		},

	};

	function GeometryParser() {}

	GeometryParser.prototype = {

		constructor: GeometryParser,

		parse( geoData, layer ) {

			var geometry = new THREE.BufferGeometry();

			geometry.addAttribute( 'position', new THREE.Float32BufferAttribute( geoData.points, 3 ) );

			var indices = this.splitIndices( geoData.vertexIndices, geoData.polygonDimensions );
			geometry.setIndex( indices );

			this.parseGroups( geometry, geoData );

			geometry.computeVertexNormals();

			this.parseUVs( geometry, layer, indices );
			this.parseMorphTargets( geometry, layer, indices );

			// TODO: z may need to be reversed to account for coordinate system change
			geometry.translate( - layer.pivot[ 0 ], - layer.pivot[ 1 ], - layer.pivot[ 2 ] );

			// var userData = geometry.userData;
			// geometry = geometry.toNonIndexed()
			// geometry.userData = userData;

			return geometry;

		},

		// split quads into tris
		splitIndices( indices, polygonDimensions ) {

			var remappedIndices = [];

			var i = 0;
			polygonDimensions.forEach( function ( dim ) {

				if ( dim < 4 ) {

					for ( var k = 0; k < dim; k ++ ) remappedIndices.push( indices[ i + k ] );

				} else if ( dim === 4 ) {

					remappedIndices.push(
						indices[ i ],
						indices[ i + 1 ],
						indices[ i + 2 ],

						indices[ i ],
						indices[ i + 2 ],
						indices[ i + 3 ]

					);

				} else if ( dim > 4 ) {

					for ( var k = 1; k < dim - 1; k ++ ) {

						remappedIndices.push( indices[ i ], indices[ i + k ], indices[ i + k + 1 ] );

					}

					console.warn( 'LWOLoader: polygons with greater than 4 sides are not supported' );

				}

				i += dim;

			} );

			return remappedIndices;

		},

		// NOTE: currently ignoring poly indices and assuming that they are intelligently ordered
		parseGroups( geometry, geoData ) {

			var tags = lwoTree.tags;
			var matNames = [];

			var elemSize = 3;
			if ( geoData.type === 'lines' ) elemSize = 2;
			if ( geoData.type === 'points' ) elemSize = 1;

			var remappedIndices = this.splitMaterialIndices( geoData.polygonDimensions, geoData.materialIndices );

			var indexNum = 0; // create new indices in numerical order
			var indexPairs = {}; // original indices mapped to numerical indices

			var prevMaterialIndex;

			var prevStart = 0;
			var currentCount = 0;

			for ( var i = 0; i < remappedIndices.length; i += 2 ) {

				var materialIndex = remappedIndices[ i + 1 ];

				if ( i === 0 ) matNames[ indexNum ] = tags[ materialIndex ];

				if ( prevMaterialIndex === undefined ) prevMaterialIndex = materialIndex;

				if ( materialIndex !== prevMaterialIndex ) {

					var currentIndex;
					if ( indexPairs[ tags[ prevMaterialIndex ] ] ) {

						currentIndex = indexPairs[ tags[ prevMaterialIndex ] ];

					} else {

						currentIndex = indexNum;
						indexPairs[ tags[ prevMaterialIndex ] ] = indexNum;
						matNames[ indexNum ] = tags[ prevMaterialIndex ];
						indexNum ++;

					}

					geometry.addGroup( prevStart, currentCount, currentIndex );

					prevStart += currentCount;

					prevMaterialIndex = materialIndex;
					currentCount = 0;

				}

				currentCount += elemSize;

			}

			// the loop above doesn't add the last group, do that here.
			if ( geometry.groups.length > 0 ) {

				var currentIndex;
				if ( indexPairs[ tags[ materialIndex ] ] ) {

					currentIndex = indexPairs[ tags[ materialIndex ] ];

				} else {

					currentIndex = indexNum;
					indexPairs[ tags[ materialIndex ] ] = indexNum;
					matNames[ indexNum ] = tags[ materialIndex ];

				}

				geometry.addGroup( prevStart, currentCount, currentIndex );

			}

			// Mat names from TAGS chunk, used to build up an array of materials for this geometry
			geometry.userData.matNames = matNames;

		},

		splitMaterialIndices( polygonDimensions, indices ) {

			var remappedIndices = [];

			polygonDimensions.forEach( function ( dim, i ) {

				if ( dim <= 3 ) {

					remappedIndices.push( indices[ i * 2 ], indices[ i * 2 + 1 ] );

				} else if ( dim === 4 ) {

					remappedIndices.push( indices[ i * 2 ], indices[ i * 2 + 1 ], indices[ i * 2 ], indices[ i * 2 + 1 ] );

				} else {

					 // ignore > 4 for now
					for ( var k = 0; k < dim - 2; k ++ ) {

						remappedIndices.push( indices[ i * 2 ], indices[ i * 2 + 1 ] );

					}

				}

			} );

			return remappedIndices;

		},

		// UV maps:
		// 1: are defined via index into an array of points, not into a geometry
		// - the geometry is also defined by an index into this array, but the indexes may not match
		// 2: there can be any number of UV maps for a single geometry. Here these are combined,
		// 	with preference given to the first map encountered
		// 3: UV maps can be partial - that is, defined for only a part of the geometry
		// 4: UV maps can be VMAP or VMAD (discontinuous, to allow for seams). In practice, most
		// UV maps are defined as partially VMAP and partially VMAD
		// VMADs are currently not supported
		parseUVs( geometry, layer ) {

			// start by creating a UV map set to zero for the whole geometry
			var remappedUVs = Array.from( Array( geometry.attributes.position.count * 2 ), function () {

				return 0;

			} );

			for ( var name in layer.uvs ) {

				var uvs = layer.uvs[ name ].uvs;
				var uvIndices = layer.uvs[ name ].uvIndices;

				uvIndices.forEach( function ( i, j ) {

					remappedUVs[ i * 2 ] = uvs[ j * 2 ];
					remappedUVs[ i * 2 + 1 ] = uvs[ j * 2 + 1 ];

				} );

			}

			geometry.addAttribute( 'uv', new THREE.Float32BufferAttribute( remappedUVs, 2 ) );

		},

		parseMorphTargets( geometry, layer ) {

			var num = 0;
			for ( var name in layer.morphTargets ) {

				var remappedPoints = geometry.attributes.position.array.slice();

				if ( ! geometry.morphAttributes.position ) geometry.morphAttributes.position = [];

				var morphPoints = layer.morphTargets[ name ].points;
				var morphIndices = layer.morphTargets[ name ].indices;
				var type = layer.morphTargets[ name ].type;

				morphIndices.forEach( function ( i, j ) {

					if ( type === 'relative' ) {

						remappedPoints[ i * 3 ] += morphPoints[ j * 3 ];
						remappedPoints[ i * 3 + 1 ] += morphPoints[ j * 3 + 1 ];
						remappedPoints[ i * 3 + 2 ] += morphPoints[ j * 3 + 2 ];

					} else {

						remappedPoints[ i * 3 ] = morphPoints[ j * 3 ];
						remappedPoints[ i * 3 + 1 ] = morphPoints[ j * 3 + 1 ];
						remappedPoints[ i * 3 + 2 ] = morphPoints[ j * 3 + 2 ];

					}

				} );

				geometry.morphAttributes.position[ num ] = new THREE.Float32BufferAttribute( remappedPoints, 3 );
				geometry.morphAttributes.position[ num ].name = name;

				num ++;

			}

		},

	};

	// parse data from the IFF buffer.
	// LWO3 files are in IFF format and can contain the following data types, referred to by shorthand codes
	//
	// ATOMIC DATA TYPES
	// ID Tag - 4x 7 bit uppercase ASCII chars: ID4
	// signed integer, 1, 2, or 4 byte length: I1, I2, I4
	// unsigned integer, 1, 2, or 4 byte length: U1, U2, U4
	// float, 4 byte length: F4
	// string, series of ASCII chars followed by null byte (If the length of the string including the null terminating byte is odd, an extra null is added so that the data that follows will begin on an even byte boundary): S0
	//
	//  COMPOUND DATA TYPES
	// Variable-length Index (index into an array or collection): U2 or U4 : VX
	// Color (RGB): F4 + F4 + F4: COL12
	// Coordinate (x, y, z): F4 + F4 + F4: VEC12
	// Percentage F4 data type from 0->1 with 1 = 100%: FP4
	// Angle in radian F4: ANG4
	// Filename (string) S0: FNAM0
	// XValue F4 + index (VX) + optional envelope( ENVL ): XVAL
	// XValue vector VEC12 + index (VX) + optional envelope( ENVL ): XVAL3
	//
	// The IFF file is arranged in chunks:
	// CHUNK = ID4 + length (U4) + length X bytes of data + optional 0 pad byte
	// optional 0 pad byte is there to ensure chunk ends on even boundary, not counted in size

	// Chunks are combined in Forms (collections of chunks)
	// FORM = string 'FORM' (ID4) + length (U4) + type (ID4) + optional ( CHUNK | FORM )

	// CHUNKS and FORMS are collectively referred to as blocks

	// The entire file is contained in one top level FORM
	function IFFParser() {}

	IFFParser.prototype = {

		constructor: IFFParser,

		parse: function ( buffer ) {

			// dump the whole buffer as a string for testing
			// printBuffer( buffer );

			this.reader = new DataViewReader( buffer );

			this.tree = {
				materials: {},
				layers: [],
				tags: [],
				textures: [],
			};

			// start out at the top level to add any data before first layer is encountered
			this.currentLayer = this.tree;
			this.currentForm = this.tree;

			// parse blocks until end of file is reached
			while ( ! this.reader.endOfFile() ) this.parseBlock();

			return this.tree;

		},

		parseBlock() {

			var blockID = this.reader.getIDTag();
			var length = this.reader.getUint32(); // size of data in bytes
			if ( this.tree.format === 'LWO2' && length > this.reader.dv.byteLength - this.reader.offset ) {

				this.reader.offset -= 4;
				length = this.reader.getUint16();

			}


			// Data types may be found in either LWO2 OR LWO3 spec
			switch ( blockID ) {

				case 'FORM': // form blocks may consist of sub -chunks or sub-forms
					this.parseForm( length );
					break;

					// SKIPPED CHUNKS

				// MISC skipped
				case 'ICON': // Thumbnail Icon Image
				case 'VMPA': // Vertex Map Parameter
				case 'BBOX': // bounding box
				// case 'VMMD':
				// case 'VTYP':

				// normal maps can be specified, normally on models imported from other applications. Currently ignored
				case 'NORM':

				// ENVL FORM skipped
				case 'PRE ':
				case 'POST':
				case 'KEY ':
				case 'SPAN':

				// CLIP FORM skipped
				case 'TIME':
				case 'CLRS':
				case 'CLRA':
				case 'FILT':
				case 'DITH':
				case 'CONT':
				case 'BRIT':
				case 'SATR':
				case 'HUE ':
				case 'GAMM':
				case 'NEGA':
				case 'IFLT':
				case 'PFLT':

				// Image Map Layer skipped
				case 'PROJ':
				case 'AXIS':
				case 'AAST':
				case 'PIXB':
				case 'STCK':

				// Procedural Textures skipped
				case 'VALU':

				// Gradient Textures skipped
				case 'PNAM':
				case 'INAM':
				case 'GRST':
				case 'GREN':
				case 'GRPT':
				case 'FKEY':
				case 'IKEY':

				// Texture Mapping Form skipped
				case 'CSYS':

					// Surface CHUNKs skipped
				case 'OPAQ': // top level 'opacity' checkbox
				case 'CMAP': // clip map

				// Surface node CHUNKS skipped
				// These mainly specify the node editor setup in LW
				case 'NLOC':
				case 'NZOM':
				case 'NVER':
				case 'NSRV':
				case 'NCRD':
				case 'NMOD':
				case 'NPRW':
				case 'NPLA':
				case 'VERS':
				case 'ENUM':
				case 'TAG ':

				// Car Material CHUNKS
				case 'CGMD':
				case 'CGTY':
				case 'CGST':
				case 'CGEN':
				case 'CGTS':
				case 'CGTE':
				case 'OSMP':
				case 'OMDE':
				case 'OUTR':
					this.reader.skip( length );
					break;

				case 'FLAG':
					if ( this.tree.format === 'LWO2' ) {

						this.reader.skip( 4 ); // not suported

					} else {

						this.reader.skip( length );

					}
					break;
				// Skipped LWO2 chunks
				case 'DIFF': // diffuse level, may be necessary to modulate COLR with this
					this.currentSurface.diffusePower = this.reader.getFloat32();
					this.reader.skip( 2 );
					break;
				case 'TRNL':
				case 'REFL':
				case 'GLOS':
				case 'SHRP':
				case 'RFOP':
				case 'RSAN':
				case 'TROP':
				case 'RBLR':
				case 'TBLR':
				case 'CLRH':
				case 'CLRF':
				case 'ADTR':
				case 'GLOW':
				case 'LINE':
				case 'ALPH':
				case 'VCOL':
				case 'ENAB':
					this.reader.skip( length );
					break;
				case 'SURF':
					if ( this.tree.format === 'LWO2' ) {

						this.parseSurfaceLwo2( length );

					}
					break;
				case 'CLIP':
					if ( this.tree.format === 'LWO2' ) {

						this.parseClipLwo2( length );

					}
					break;
				// Texture node chunks (not in spec)
				case 'IPIX': // usePixelBlending
				case 'IMIP': // useMipMaps
				case 'IMOD': // imageBlendingMode
				case 'AMOD': // unknown
				case 'IINV': // imageInvertAlpha
				case 'INCR': // imageInvertColor
				case 'IAXS': // imageAxis ( for non-UV maps)
				case 'IFOT': // imageFallofType
				case 'ITIM': // timing for animated textures
				case 'IWRL':
				case 'IUTI':
				case 'IINX':
				case 'IINY':
				case 'IINZ':
				case 'IREF': // possibly a VX for reused texture nodes
					if ( length === 4 ) this.currentNode[ blockID ] = this.reader.getInt32();
					else this.reader.skip( length );
					break;

				case 'OTAG':
					this.parseObjectTag();
					break;

				case 'LAYR':
					this.parseLayer( length );
					break;

				case 'PNTS':
					this.parsePoints( length );
					break;

				case 'VMAP':
					this.parseVertexMapping( length );
					break;

				case 'POLS':
					this.parsePolygonList( length );
					break;

				case 'TAGS':
					this.parseTagStrings( length );
					break;

				case 'PTAG':
					this.parsePolygonTagMapping( length );
					break;

				case 'VMAD':
					this.parseVertexMapping( length, true );
					break;

				// Misc CHUNKS
				case 'DESC': // Description Line
					this.currentForm.description = this.reader.getString();
					break;

				case 'TEXT':
				case 'CMNT':
				case 'NCOM':
					this.currentForm.comment = this.reader.getString();
					break;

					// Envelope Form
				case 'NAME':
					this.currentForm.channelName = this.reader.getString();
					break;

					// Image Map Layer

				case 'WRAP':
					this.currentForm.wrap = { w: this.reader.getUint16(), h: this.reader.getUint16() };
					break;

				case 'IMAG':
					var index = this.reader.getVariableLengthIndex();
					this.currentForm.imageIndex = index;
					break;

					// Texture Mapping Form

				case 'OREF':
					this.currentForm.referenceObject = this.reader.getString();
					break;

				case 'ROID':
					this.currentForm.referenceObjectID = this.reader.getUint32();
					break;

					// Surface Blocks

				case 'SSHN':
					this.currentSurface.surfaceShaderName = this.reader.getString();
					break;

				case 'AOVN':
					this.currentSurface.surfaceCustomAOVName = this.reader.getString();
					break;

					// Nodal Blocks

				case 'NSTA':
					this.currentForm.disabled = this.reader.getUint16();
					break;

				case 'NRNM':
					this.currentForm.realName = this.reader.getString();
					break;

				case 'NNME':
					this.currentForm.refName = this.reader.getString();
					this.currentSurface.nodes[ this.currentForm.refName ] = this.currentForm;
					break;

				// Nodal Blocks : connections
				case 'INME':
					if ( ! this.currentForm.nodeName ) this.currentForm.nodeName = [];
					this.currentForm.nodeName.push( this.reader.getString() );
					break;

				case 'IINN':
					if ( ! this.currentForm.inputNodeName ) this.currentForm.inputNodeName = [];
					this.currentForm.inputNodeName.push( this.reader.getString() );
					break;

				case 'IINM':
					if ( ! this.currentForm.inputName ) this.currentForm.inputName = [];
					this.currentForm.inputName.push( this.reader.getString() );
					break;

				case 'IONM':
					if ( ! this.currentForm.inputOutputName ) this.currentForm.inputOutputName = [];
					this.currentForm.inputOutputName.push( this.reader.getString() );
					break;

				case 'FNAM':
					this.currentForm.fileName = this.reader.getString();
					break;

				case 'CHAN': // NOTE: ENVL Forms may also have CHAN chunk, however ENVL is currently ignored
					if ( length === 4 ) this.currentForm.textureChannel = this.reader.getIDTag();
					else this.reader.skip( length );
					break;

					// LWO2 Spec chunks: these are needed since the SURF FORMs are often in LWO2 format

				case 'SMAN':
					var maxSmoothingAngle = this.reader.getFloat32();
					this.currentSurface.attributes.smooth = ( maxSmoothingAngle < 0 ) ? false : true;
					break;

				// LWO2: Basic Surface Parameters
				case 'COLR':
					this.currentSurface.attributes.Color = {};
					this.currentSurface.attributes.Color.value = this.reader.getFloat32Array( 3 );
					this.reader.skip( 2 ); // VX: envelope
					break;

				case 'LUMI':
					this.currentSurface.attributes.luminosityLevel = this.reader.getFloat32();
					this.reader.skip( 2 );
					break;

				case 'SPEC':
					this.currentSurface.attributes.specularLevel = this.reader.getFloat32();
					this.reader.skip( 2 );
					break;

				case 'TRAN':
					this.currentSurface.attributes.opacity = this.reader.getFloat32();
					this.reader.skip( 2 );
					break;

				case 'BUMP':
					this.currentSurface.attributes.bumpStrength = this.reader.getFloat32();
					this.reader.skip( 2 );
					break;

				case 'SIDE':
					this.currentSurface.attributes.side = this.reader.getUint16();
					break;

				case 'RIMG':
					this.currentSurface.attributes.reflectionMap = this.reader.getVariableLengthIndex();
					break;

				case 'RIND':
					this.currentSurface.attributes.refractiveIndex = this.reader.getFloat32();
					this.reader.skip( 2 );
					break;

				case 'TIMG':
					this.currentSurface.attributes.refractionMap = this.reader.getVariableLengthIndex();
					break;

				case 'IMAP':
					if ( this.tree.format === 'LWO2' ) {

						this.reader.skip( 2 );

					} else {

						this.currentSurface.attributes.imageMapIndex = this.reader.getUint32();

					}
					break;

				case 'IUVI': // uv channel name
					this.currentNode.UVChannel = this.reader.getString( length );
					break;

				case 'IUTL': // widthWrappingMode: 0 = Reset, 1 = Repeat, 2 = Mirror, 3 = Edge
					this.currentNode.widthWrappingMode = this.reader.getUint32();
					break;
				case 'IVTL': // heightWrappingMode
					this.currentNode.heightWrappingMode = this.reader.getUint32();
					break;

				// LWO2 USE
				case 'BLOK':
					// skip
					break;

				default:
					this.parseUnknownCHUNK( blockID, length );

			}

			if ( this.reader.offset >= this.currentFormEnd ) {

				this.currentForm = this.parentForm;

			}

		},


		///
		// FORM PARSING METHODS
		///

		// Forms are organisational and can contain any number of sub chunks and sub forms
		// FORM ::= 'FORM'[ID4], length[U4], type[ID4], ( chunk[CHUNK] | form[FORM] ) * }
		parseForm( length ) {

			var type = this.reader.getIDTag();

			switch ( type ) {

				// SKIPPED FORMS
				// if skipForm( length ) is called, the entire form and any sub forms and chunks are skipped

				case 'ISEQ': // Image sequence
				case 'ANIM': // plug in animation
				case 'STCC': // Color-cycling Still
				case 'VPVL':
				case 'VPRM':
				case 'NROT':
				case 'WRPW': // image wrap w ( for cylindrical and spherical projections)
				case 'WRPH': // image wrap h
				case 'FUNC':
				case 'FALL':
				case 'OPAC':
				case 'GRAD': // gradient texture
				case 'ENVS':
				case 'VMOP':
				case 'VMBG':

				// Car Material FORMS
				case 'OMAX':
				case 'STEX':
				case 'CKBG':
				case 'CKEY':
				case 'VMLA':
				case 'VMLB':
					this.skipForm( length ); // not currently supported
					break;

				// if break; is called directly, the position in the lwoTree is not created
				// any sub chunks and forms are added to the parent form instead
				case 'META':
				case 'NNDS':
				case 'NODS':
				case 'NDTA':
				case 'ADAT':
				case 'AOVS':
				case 'BLOK':

				// used by texture nodes
				case 'IBGC': // imageBackgroundColor
				case 'IOPC': // imageOpacity
				case 'IIMG': // hold reference to image path
				case 'TXTR':
					// this.setupForm( type, length );
					break;

				case 'IFAL': // imageFallof
				case 'ISCL': // imageScale
				case 'IPOS': // imagePosition
				case 'IROT': // imageRotation
				case 'IBMP':
				case 'IUTD':
				case 'IVTD':
					this.parseTextureNodeAttribute( type );
					break;

				case 'LWO2':
					this.tree.format = type;
					break;

				case 'LWO3':
					this.tree.format = type;
					break;

				case 'ENVL':
					this.parseEnvelope( length );
					break;

					// CLIP FORM AND SUB FORMS

				case 'CLIP':
					if ( this.tree.format === 'LWO2' ) {

						this.parseForm( length );

					} else {

						this.parseClip( length );

					}
					break;

				case 'STIL':
					this.parseImage();
					break;

				case 'XREF': // clone of another STIL
					this.reader.skip( 8 ); // unknown
					this.currentForm.referenceTexture = {
						index: this.reader.getUint32(),
						refName: this.reader.getString() // internal unique ref
					};
					break;

					// Not in spec, used by texture nodes

				case 'IMST':
					this.parseImageStateForm( length );
					break;

					// SURF FORM AND SUB FORMS

				case 'SURF':
					this.parseSurfaceForm( length );
					break;

				case 'VALU': // Not in spec
					this.parseValueForm( length );
					break;

				case 'NTAG':
					this.parseSubNode( length );
					break;

				case 'ATTR': // BSDF Node Attributes
				case 'SATR': // Standard Node Attributes
					this.setupForm( 'attributes', length );
					break;

				case 'NCON':
					this.parseConnections( length );
					break;

				case 'SSHA':
					this.parentForm = this.currentForm;
					this.currentForm = this.currentSurface;
					this.setupForm( 'surfaceShader', length );
					break;

				case 'SSHD':
					this.setupForm( 'surfaceShaderData', length );
					break;

				case 'ENTR': // Not in spec
					this.parseEntryForm( length );
					break;

					// Image Map Layer

				case 'IMAP':
					this.parseImageMap( length );
					break;

				case 'TAMP':
					this.parseXVAL( 'amplitude', length );
					break;

					//Texture Mapping Form

				case 'TMAP':
					this.setupForm( 'textureMap', length );
					break;

				case 'CNTR':
					this.parseXVAL3( 'center', length );
					break;

				case 'SIZE':
					this.parseXVAL3( 'scale', length );
					break;

				case 'ROTA':
					this.parseXVAL3( 'rotation', length );
					break;

				default:
					this.parseUnknownForm( type, length );

			}

		},

		setupForm( type, length ) {

			if ( ! this.currentForm ) this.currentForm = this.currentNode;

			this.currentFormEnd = this.reader.offset + length;
			this.parentForm = this.currentForm;

			if ( ! this.currentForm[ type ] ) {

				this.currentForm[ type ] = {};
				this.currentForm = this.currentForm[ type ];


			} else {

				// should never see this unless there's a bug in the reader
				console.warn( 'LWOLoader: form already exists on parent: ', type, this.currentForm );

				this.currentForm = this.currentForm[ type ];

			}


		},

		skipForm( length ) {

			this.reader.skip( length - 4 );

		},

		parseUnknownForm( type, length ) {

			console.warn( 'LWOLoader: unknown FORM encountered: ' + type, length );

			printBuffer( this.reader.dv.buffer, this.reader.offset, length - 4 );
			this.reader.skip( length - 4 );

		},

		parseSurfaceForm( length ) {

			this.reader.skip( 8 ); // unknown Uint32 x2

			var name = this.reader.getString();

			var surface = {
				attributes: {}, // LWO2 style non-node attributes will go here
				connections: {},
				name: name,
				inputName: name,
				nodes: {},
				source: this.reader.getString(),
			};

			this.tree.materials[ name ] = surface;
			this.currentSurface = surface;

			this.parentForm = this.tree.materials;
			this.currentForm = surface;
			this.currentFormEnd = this.reader.offset + length;

		},

		parseSurfaceLwo2( length ) {

			var firstOffset = this.reader.offset;
			var name = this.reader.getString();

			var surface = {
				attributes: {}, // LWO2 style non-node attributes will go here
				connections: {},
				name: name,
				nodes: {},
				source: this.reader.getString(),
			};

			this.tree.materials[ name ] = surface;
			this.currentSurface = surface;

			this.parentForm = this.tree.materials;
			this.currentForm = surface;
			this.currentFormEnd = this.reader.offset + length;

		},

		parseSubNode( length ) {

			// parse the NRNM CHUNK of the subnode FORM to get
			// a meaningful name for the subNode
			// some subnodes can be renamed, but Input and Surface cannot

			this.reader.skip( 8 ); // NRNM + length
			var name = this.reader.getString();

			var node = {
				name: name
			};
			this.currentForm = node;
			this.currentNode = node;

			this.currentFormEnd = this.reader.offset + length;


		},

		// collect attributes from all nodes at the top level of a surface
		parseConnections( length ) {

			this.currentFormEnd = this.reader.offset + length;
			this.parentForm = this.currentForm;

			this.currentForm = this.currentSurface.connections;

		},

		// surface node attribute data, e.g. specular, roughness etc
		parseEntryForm( length ) {

			this.reader.skip( 8 ); // NAME + length
			var name = this.reader.getString();
			this.currentForm = this.currentNode.attributes;

			this.setupForm( name, length );

		},

		// parse values from material - doesn't match up to other LWO3 data types
		// sub form of entry form
		parseValueForm() {

			this.reader.skip( 8 ); // unknown + length

			var valueType = this.reader.getString();

			if ( valueType === 'double' ) {

				this.currentForm.value = this.reader.getUint64();

			} else if ( valueType === 'int' ) {

				this.currentForm.value = this.reader.getUint32();

			} else if ( valueType === 'vparam' ) {

				this.reader.skip( 24 );
				this.currentForm.value = this.reader.getFloat64();

			} else if ( valueType === 'vparam3' ) {

				this.reader.skip( 24 );
				this.currentForm.value = this.reader.getFloat64Array( 3 );


			}

		},

		// holds various data about texture node image state
		// Data other thanmipMapLevel unknown
		parseImageStateForm() {

			this.reader.skip( 8 ); // unknown

			this.currentForm.mipMapLevel = this.reader.getFloat32();

		},

		// LWO2 style image data node OR LWO3 textures defined at top level in editor (not as SURF node)
		parseImageMap( length ) {

			this.currentFormEnd = this.reader.offset + length;
			this.parentForm = this.currentForm;

			if ( ! this.currentForm.maps ) this.currentForm.maps = [];

			var map = {};
			this.currentForm.maps.push( map );
			this.currentForm = map;

			this.reader.skip( 10 ); // unknown, could be an issue if it contains a VX

		},

		parseTextureNodeAttribute( type ) {

			this.reader.skip( 28 ); // FORM + length + VPRM + unknown + Uint32 x2 + float32

			this.reader.skip( 20 ); // FORM + length + VPVL + float32 + Uint32

			switch ( type ) {

				case 'ISCL':
					this.currentNode.scale = this.reader.getFloat32Array( 3 );
					break;
				case 'IPOS':
					this.currentNode.position = this.reader.getFloat32Array( 3 );
					break;
				case 'IROT':
					this.currentNode.rotation = this.reader.getFloat32Array( 3 );
					break;
				case 'IFAL':
					this.currentNode.falloff = this.reader.getFloat32Array( 3 );
					break;

				case 'IBMP':
					this.currentNode.amplitude = this.reader.getFloat32();
					break;
				case 'IUTD':
					this.currentNode.uTiles = this.reader.getFloat32();
					break;
				case 'IVTD':
					this.currentNode.vTiles = this.reader.getFloat32();
					break;

			}

			this.reader.skip( 2 ); // unknown


		},

		// ENVL forms are currently ignored
		parseEnvelope( length ) {

			this.reader.skip( length - 4 ); // skipping  entirely for now

		},

		///
		// CHUNK PARSING METHODS
		///

		// clips can either be defined inside a surface node, or at the top
		// level and they have a different format in each case
		parseClip( length ) {

			var tag = this.reader.getIDTag();

			// inside surface node
			if ( tag === 'FORM' ) {

				this.reader.skip( 16 );

				this.currentNode.fileName = this.reader.getString();

				return;

			}

			// otherwise top level
			this.reader.setOffset( this.reader.offset - 4 );

			this.currentFormEnd = this.reader.offset + length;
			this.parentForm = this.currentForm;

			this.reader.skip( 8 ); // unknown

			var texture = {
				index: this.reader.getUint32()
			};
			this.tree.textures.push( texture );
			this.currentForm = texture;

		},

		parseClipLwo2( length ) {

			var texture = {
				index: this.reader.getUint32(),
				fileName: ""
			};

			var readed = 4;
			// seach STIL block
			while ( true ) {

				var tag = this.reader.getIDTag();
				var n_length = this.reader.getUint16();
				if ( tag === 'STIL' ) {

					texture.fileName = this.reader.getString();
					break;

				}
				readed += 4 + n_length;
				if ( n_length >= length ) {

					break;

				}

			}

			this.tree.textures.push( texture );
			this.currentForm = texture;

		},

		parseImage() {

			this.reader.skip( 8 ); // unknown
			this.currentForm.fileName = this.reader.getString();

		},

		parseXVAL( type, length ) {

			var endOffset = this.reader.offset + length - 4;
			this.reader.skip( 8 );

			this.currentForm[ type ] = this.reader.getFloat32();

			this.reader.setOffset( endOffset ); // set end offset directly to skip optional envelope

		},

		parseXVAL3( type, length ) {

			var endOffset = this.reader.offset + length - 4;
			this.reader.skip( 8 );

			this.currentForm[ type ] = {
				x: this.reader.getFloat32(),
				y: this.reader.getFloat32(),
				z: this.reader.getFloat32(),
			};

			this.reader.setOffset( endOffset );

		},

		// Tags associated with an object
		// OTAG { type[ID4], tag-string[S0] }
		parseObjectTag() {

			if ( ! this.tree.objectTags ) this.tree.objectTags = {};

			this.tree.objectTags[ this.reader.getIDTag() ] = {
				tagString: this.reader.getString()
			};

		},

		// Signals the start of a new layer. All the data chunks which follow will be included in this layer until another layer chunk is encountered.
		// LAYR: number[U2], flags[U2], pivot[VEC12], name[S0], parent[U2]
		parseLayer( length ) {

			var layer = {
				number: this.reader.getUint16(),
				flags: this.reader.getUint16(), // If the least significant bit of flags is set, the layer is hidden.
				pivot: this.reader.getFloat32Array( 3 ), // Note: this seems to be superflous, as the geometry is translated when pivot is present
				name: this.reader.getString(),
			};

			this.tree.layers.push( layer );
			this.currentLayer = layer;

			var parsedLength = 16 + stringOffset( this.currentLayer.name ); // index ( 2 ) + flags( 2 ) + pivot( 12 ) + stringlength

			// if we have not reached then end of the layer block, there must be a parent defined
			this.currentLayer.parent = ( parsedLength < length ) ? this.reader.getUint16() : - 1; // omitted or -1 for no parent

		},

		// VEC12 * ( F4 + F4 + F4 ) array of x,y,z vectors
		// Converting from left to right handed coordinate system:
		// x -> -x and switch material FrontSide -> BackSide
		parsePoints( length ) {

			this.currentPoints = [];
			for ( var i = 0; i < length / 4; i += 3 ) {

				// z -> -z to match three.js right handed coords
				this.currentPoints.push( this.reader.getFloat32(), this.reader.getFloat32(), - this.reader.getFloat32() );

			}

		},

		// parse VMAP or VMAD
		// Associates a set of floating-point vectors with a set of points.
		// VMAP: { type[ID4], dimension[U2], name[S0], ( vert[VX], value[F4] # dimension ) * }

		// VMAD Associates a set of floating-point vectors with the vertices of specific polygons.
		// Similar to VMAP UVs, but associates with polygon vertices rather than points
		// to solve to problem of UV seams:  VMAD chunks are paired with VMAPs of the same name,
		// if they exist. The vector values in the VMAD will then replace those in the
		// corresponding VMAP, but only for calculations involving the specified polygons.
		// VMAD { type[ID4], dimension[U2], name[S0], ( vert[VX], poly[VX], value[F4] # dimension ) * }
		parseVertexMapping( length, discontinuous ) {

			var finalOffset = this.reader.offset + length;

			var channelName = this.reader.getString();

			if ( this.reader.offset === finalOffset ) {

				// then we are in a texture node and the VMAP chunk is just a reference to a UV channel name
				this.currentForm.UVChannel = channelName;
				return;

			}

			// otherwise reset to initial length and parse normal VMAP CHUNK
			this.reader.setOffset( this.reader.offset - stringOffset( channelName ) );

			var type = this.reader.getIDTag();

			this.reader.getUint16(); // dimension
			var name = this.reader.getString();

			var remainingLength = length - 6 - stringOffset( name );

			switch ( type ) {

				case 'TXUV':
					this.parseUVMapping( name, finalOffset, discontinuous );
					break;
				case 'MORF':
				case 'SPOT':
					this.parseMorphTargets( name, finalOffset, type ); // can't be discontinuous
					break;
				// unsupported VMAPs
				case 'APSL':
				case 'NORM':
				case 'WGHT':
				case 'MNVW':
				case 'PICK':
				case 'RGB ':
				case 'RGBA':
					this.reader.skip( remainingLength );
					break;
				default:
					console.warn( 'LWOLoader: unknown vertex map type: ' + type );
					this.reader.skip( remainingLength );

			}

		},

		parseUVMapping( name, finalOffset, discontinuous ) {

			var uvIndices = [];
			var polyIndices = [];
			var uvs = [];

			while ( this.reader.offset < finalOffset ) {

				uvIndices.push( this.reader.getVariableLengthIndex() );

				if ( discontinuous ) polyIndices.push( this.reader.getVariableLengthIndex() );

				uvs.push( this.reader.getFloat32(), this.reader.getFloat32() );

			}

			if ( discontinuous ) {

				if ( ! this.currentLayer.discontinuousUVs ) this.currentLayer.discontinuousUVs = {};

				this.currentLayer.discontinuousUVs[ name ] = {
					uvIndices: uvIndices,
					polyIndices: polyIndices,
					uvs: uvs,
				};

			} else {

				if ( ! this.currentLayer.uvs ) this.currentLayer.uvs = {};

				this.currentLayer.uvs[ name ] = {
					uvIndices: uvIndices,
					uvs: uvs,
				};

			}

		},

		parseMorphTargets( name, finalOffset, type ) {

			var indices = [];
			var points = [];

			type = ( type === 'MORF' ) ? 'relative' : 'absolute';

			while ( this.reader.offset < finalOffset ) {

				indices.push( this.reader.getVariableLengthIndex() );
				// z -> -z to match three.js right handed coords
				points.push( this.reader.getFloat32(), this.reader.getFloat32(), - this.reader.getFloat32() );

			}

			if ( ! this.currentLayer.morphTargets ) this.currentLayer.morphTargets = {};

			this.currentLayer.morphTargets[ name ] = {
				indices: indices,
				points: points,
				type: type,
			};

		},

		// A list of polygons for the current layer.
		// POLS { type[ID4], ( numvert+flags[U2], vert[VX] # numvert ) * }
		parsePolygonList( length ) {

			var finalOffset = this.reader.offset + length;
			var type = this.reader.getIDTag();

			var indices = [];

			// hold a list of polygon sizes, to be split up later
			var polygonDimensions = [];

			while ( this.reader.offset < finalOffset ) {

				var numverts = this.reader.getUint16();

				//var flags = numverts & 64512; // 6 high order bits are flags - ignoring for now
				numverts = numverts & 1023; // remaining ten low order bits are vertex num
				polygonDimensions.push( numverts );

				for ( var j = 0; j < numverts; j ++ ) indices.push( this.reader.getVariableLengthIndex() );

			}

			var geometryData = {
				type: type,
				vertexIndices: indices,
				polygonDimensions: polygonDimensions,
				points: this.currentPoints
			};

			// Note: assuming that all polys will be lines or points if the first is
			if ( polygonDimensions[ 0 ] === 1 ) geometryData.type = 'points';
			else if ( polygonDimensions[ 0 ] === 2 ) geometryData.type = 'lines';

			this.currentLayer.geometry = geometryData;

		},

		// Lists the tag strings that can be associated with polygons by the PTAG chunk.
		// TAGS { tag-string[S0] * }
		parseTagStrings( length ) {

			this.tree.tags = this.reader.getStringArray( length );

		},

		// Associates tags of a given type with polygons in the most recent POLS chunk.
		// PTAG { type[ID4], ( poly[VX], tag[U2] ) * }
		parsePolygonTagMapping( length ) {

			var finalOffset = this.reader.offset + length;
			var type = this.reader.getIDTag();
			if ( type === 'SURF' ) this.parseMaterialIndices( finalOffset );
			else { //PART, SMGP, COLR not supported

				this.reader.skip( length - 4 );

			}

		},

		parseMaterialIndices( finalOffset ) {

			// array holds polygon index followed by material index
			this.currentLayer.geometry.materialIndices = [];

			var initialMatIndex;

			while ( this.reader.offset < finalOffset ) {

				var polygonIndex = this.reader.getVariableLengthIndex();
				var materialIndex = this.reader.getUint16();

				if ( ! initialMatIndex ) initialMatIndex = materialIndex; // set up first mat index

				this.currentLayer.geometry.materialIndices.push( polygonIndex, materialIndex );

			}

		},

		parseUnknownCHUNK( blockID, length ) {

			console.warn( 'LWOLoader: unknown chunk type: ' + blockID + ' length: ' + length );

			// print the chunk plus some bytes padding either side
			// printBuffer( this.reader.dv.buffer, this.reader.offset - 20, length + 40 );

			var data = this.reader.getString( length );

			this.currentForm[ blockID ] = data;

		}

	};

	function DataViewReader( buffer ) {

		// For testing: dump whole buffer to console as a string
		// printBuffer( buffer, 0, buffer.byteLength );

		this.dv = new DataView( buffer );
		this.offset = 0;

	}

	DataViewReader.prototype = {

		constructor: DataViewReader,

		size: function () {

			return this.dv.buffer.byteLength;

		},

		setOffset( offset ) {

			if ( offset > 0 && offset < this.dv.buffer.byteLength ) {

				this.offset = offset;

			} else {

				console.error( 'LWOLoader: invalid buffer offset' );

			}

		},

		endOfFile: function () {

			if ( this.offset >= this.size() ) return true;
			return false;

		},

		skip: function ( length ) {

			this.offset += length;

		},

		getUint8: function () {

			var value = this.dv.getUint8( this.offset );
			this.offset += 1;
			return value;

		},

		getUint16: function () {

			var value = this.dv.getUint16( this.offset );
			this.offset += 2;
			return value;

		},

		getInt32: function () {

			var value = this.dv.getInt32( this.offset, false );
			this.offset += 4;
			return value;

		},

		getUint32: function () {

			var value = this.dv.getUint32( this.offset, false );
			this.offset += 4;
			return value;

		},

		getUint64: function () {

			var low, high;

			high = this.getUint32();
			low = this.getUint32();
			return high * 0x100000000 + low;

		},

		getFloat32: function () {

			var value = this.dv.getFloat32( this.offset, false );
			this.offset += 4;
			return value;

		},

		getFloat32Array: function ( size ) {

			var a = [];

			for ( var i = 0; i < size; i ++ ) {

				a.push( this.getFloat32() );

			}

			return a;

		},

		getFloat64: function () {

			var value = this.dv.getFloat64( this.offset, this.littleEndian );
			this.offset += 8;
			return value;

		},

		getFloat64Array: function ( size ) {

			var a = [];

			for ( var i = 0; i < size; i ++ ) {

				a.push( this.getFloat64() );

			}

			return a;

		},

		// get variable-length index data type
		// VX ::= index[U2] | (index + 0xFF000000)[U4]
		// If the index value is less than 65,280 (0xFF00),then VX === U2
		// otherwise VX === U4 with bits 24-31 set
		// When reading an index, if the first byte encountered is 255 (0xFF), then
		// the four-byte form is being used and the first byte should be discarded or masked out.
		getVariableLengthIndex() {

			var firstByte = this.getUint8();

			if ( firstByte === 255 ) {

				return this.getUint8() * 65536 + this.getUint8() * 256 + this.getUint8();

			}

			return firstByte * 256 + this.getUint8();

		},

		// An ID tag is a sequence of 4 bytes containing 7-bit ASCII values
		getIDTag() {

			return this.getString( 4 );

		},

		getString: function ( size ) {

			if ( size === 0 ) return;

			// note: safari 9 doesn't support Uint8Array.indexOf; create intermediate array instead
			var a = [];

			if ( size ) {

				for ( var i = 0; i < size; i ++ ) {

					a[ i ] = this.getUint8();

				}

			} else {

				var currentChar;
				var len = 0;

				while ( currentChar !== 0 ) {

					currentChar = this.getUint8();
					if ( currentChar !== 0 ) a.push( currentChar );
					len ++;

				}

				if ( ! isEven( len + 1 ) ) this.getUint8(); // if string with terminating nullbyte is uneven, extra nullbyte is added

			}

			return THREE.LoaderUtils.decodeText( new Uint8Array( a ) );

		},

		getStringArray: function ( size ) {

			var a = this.getString( size );
			a = a.split( '\0' );

			return a.filter( Boolean ); // return array with any empty strings removed

		}

	};

	// ************** UTILITY FUNCTIONS **************

	function isEven( num ) {

		return num % 2;

	}

	// calculate the length of the string in the buffer
	// this will be string.length + nullbyte + optional padbyte to make the length even
	function stringOffset( string ) {

		return string.length + 1 + ( isEven( string.length + 1 ) ? 1 : 0 );

	}

	// for testing purposes, dump buffer to console
	// printBuffer( this.reader.dv.buffer, this.reader.offset, length );
	function printBuffer( buffer, from, to ) {

		console.log( THREE.LoaderUtils.decodeText( new Uint8Array( buffer, from, to ) ) );

	}

	return LWOLoader;

} )();